Twig Blight (Scab)
Venturia spp. or Fusicladium spp. (specific oak pathogen uncertain)
11 host plants
Last updated
Oak (Quercus phellos) develops shoot blight with brown lesions on young leaves and twigs, causing branch dieback during wet springs. Pathogen identity is uncertain. Prune out infected branches and avoid overhead watering. Fungicides similar to apple scab treatments may help if applied at bud break during wet periods, though efficacy data is limited.
Remove blighted tissue promptly, cutting well below visible symptoms. Improve air circulation by thinning dense growth. Avoid overhead watering, especially during bloom and new growth periods when tissues are most susceptible. For recurring problems, preventive fungicide applications timed to protect new growth can reduce infection, but cultural controls should be your first approach.
Quick Reference
Management
Wet, humid, mild spring conditions; cool temperatures; high moisture promote spore germination and infection
Cultural Controls
- Purchase healthy planting material and/or do not use plants with injured branches. Prune out, remove, and destroy infected and dead branches. Prune 5 to 6 inches below symptoms. Avoid wounding or injuring plants. Encourage plants to harden off in winter to avoid frost damage. Provide adequate plant spacing and manage canopy size to promote good air